This invention relates generally to controlling the relative angular relationship between two elements in a rotating system by changing the relationship between two elements in a related non-rotating system, such that the relative angular relationship between the two elements in the rotating system may easily be altered while the system rotates. More specifically, the present invention provides the ability to either incrementally or continuously alter the angular relationship between two parallel output shafts by introducing a specified angular motion change (angular displacement). Essentially, the two output shafts will, when left alone, rotate together at the same speed, but with the present invention, a user may introduce an angular motion change while the shafts continue to rotate, advancing one shaft""s angular position with respect to the other shaft, using a control mechanism in a static reference frame; once the user stops introducing an angular motion change, the two shafts will again rotate together at the same speed, although the angular displacement introduced will remain. In the prior art, there were two techniques for accomplishing this goal: 1) inducing lateral motion in a shaft at the center of rotation of the system, with said motion parallel and congruent to the center of rotation, and then translating that motion into the rotating system using a rotating disk sliding through bearings on levers fixed to the rotating system, or 2) varying the pressure in a hydraulic system, with said hydraulic system translated into the rotating system through a rotating seal, such that the pressure is then utilized to move an element or elements in the rotating system.
There are, however, problems inherent in these previous techniques which limit their effectiveness. Specifically, devices which use these techniques have inherently high wear factors and/or are subject to high manufacturing and maintenance costs because of the close tolerances required and the high stresses placed upon the individual components of the devices. Additionally, as these devices wear, they tend to become more unstable. The rotating disk used in the first technique described above must be able to handle all of the torque induced through the system. Because of the high relative motion of the disk to the rotating system, the rate of wear will be high and, with wear, the system will tend to oscillate. And, the hydraulic-based systems described above are inherently unstable since they do not consist of a direct mechanical coupling. Minute variations in any part of the system will impact the pressure within the hydraulic fluid and will alter the position of the driven elements, with this altering of position then changing the pressure in the hydraulic fluid to initiate positive feedback and cause, or perpetuate, an oscillation.
The present invention overcomes these problems because it employs a direct mechanical coupling which allows for control of the relative angular position of two elements in the rotating system, while such control is induced in or between two static elements outside of the rotating system. Since the present invention uses gears (with meshing teeth) for a direct mechanical coupling, the forces are spread effectively throughout the device, reducing both wear and oscillation concerns.
The Angular Motion Translator (xe2x80x9cAMTxe2x80x9d) consists conceptually of two inertial frames: a static reference frame, which is static relative to the observer, and a rotating frame, which rotates about an axis with respect to the static reference frame and the observer. The AMT can be used to translate an angular relationship between two elements contained within the static reference frame into a proportional angular relationship between two elements contained within the rotating frame. More specifically, an angular (rotational) displacement of one of the elements in the static reference frame with respect to the other element in the static reference frame will result in a proportional angular (rotational) displacement of one of the elements in the rotating frame with respect to the other element in the rotating frame, allowing a user of the AMT to easily alter the angular relationship between the two elements in the rotating frame.
The physical embodiments of the AMT are comprised of two linked, identical planetary gear sets. Each planetary gear set is comprised of a sun gear, a planetary gear array (further comprised of one or more planet gears and a planetary carrier which links the planet gears together and which fixes their orbit around the sun gear and the central axis of the planetary gear set), and an annular gear. In such planetary gear sets, the sun gear is located at the center (on the central axis of the planetary gear set), the planet gears rotate around the outside of the sun gear in orbit (with the teeth of each planet gear meshing with the teeth of the sun gear, forming a mechanical coupling), the planetary carrier links the axis of rotation of each of the planet gears and holds the planet gears together in orbit about the sun gear (such that the planetary gear array rotates as a unit), and the annular gear encompasses the whole (with the teeth of the planet gears meshing with the teeth of the annular gear, forming a mechanical coupling).
In the AMT, the two identical planetary gear sets face one another as mirror images. One of the elements of the first planetary gear set is held static, and the identical, matching element in the second planetary gear set is also held static, although the angular relationship between them may be changed. These two elements are in the static reference frame. A different element of the first planetary gear set is rigidly attached to the input shaft, with the input shaft passing through the entire AMT along the center axis (passing through the second planetary gear set without interacting with the second planetary gear set) and emerging as the inner output shaft, and the identical, matching element in the second planetary gear set is rigidly attached to the outer output shaft, which is hollow so that it does not interact with the inner output shaft. The inner output shaft and the outer output shaft are the two elements in the rotating frame. Finally, the remaining elements in both of the planetary gear sets are rigidly linked together so that they rotate as one unit. In this configuration, a change in the angular relationship between the two elements in the static reference frame produces a proportional change in the angular relationship between the two elements in the rotating frame.
So in static mode, when the input shaft rotates to provide driving power, both the inner output shaft (which is essentially a continuation of the input shaft) and the outer output shaft will rotate at the same angular speed (i.e. there will be no angular displacement). If, however, one of the elements which is being held static is rotated with respect to the other element which is being held static in the other planetary gear set, this introduces an angular displacement (either adding or subtracting a proportion of the amount of rotation between the two static elements in the static reference frame to the input rotation, resulting in a change to the outer output shaft rotation). Thus, the angular relationship between the inner output shaft and the outer output shaft may be altered proportionately by rotating one of the static elements with respect to the other.
Although the two planetary gear sets could be connected in any number of ways (so long as identical, matching elements in each planetary gear set are held static; another element in the first planetary gear set is rigidly connected to its sister, identical, matching element in the second planetary gear set; the remaining elements are connected to either the input shaft and the inner output shaft or the outer output shaft respectively; and the matching gears of each of the planetary gear sets are identical in size and number of teeth), there are two preferred embodiments which simplify construction due to convenient bearing placement. In the first embodiment, the input shaft is rigidly attached to the sun gear of the first planetary gear set, such that when the input shaft rotates, it causes the sun gear of the first planetary gear set to rotate. The sun gear of the first planetary gear set is also rigidly attached to the inner output shaft, such that the sun gear of the first planetary gear set is sandwiched between the input shaft and the inner output shaft (or, these three elements may be thought of as one, continuous element). The planet gears of the first planetary gear set orbit the sun gear with meshing teeth. The annular gear of the first planetary gear set encompasses the first planetary gear set, with its teeth meshing with those of the planet gears, and it is held static. The planetary carrier for the first planetary gear set is rigidly attached to the planetary carrier for the second planetary gear set, such that the planetary gear array (comprised of the planet gears and the planetary carrier) of the first planetary gear set and the planetary gear array (comprised of the planet gears and the planetary carrier) of the second planetary gear set are linked and rotate as a unit. The planetary gear arrays typically each have an equal number of planet gears, and the rotating axis of pairs of planet gears matched between the two planetary gear arrays are often fixed into a mounting-bearing assembly that is free to rotate about the primary axis (i.e. the planetary carriers of the first planetary gear set and the second planetary gear set are linked in such a way that they rest on bearings that allow them to freely rotate about the inner output shaft without interacting with the inner output shaft as it passes from the first planetary gear set on through the second planetary gear set). The annular gear for the second planetary gear set is also held static, with its teeth meshing with those of the planet gears of the second planetary gear set, which it encompasses. The planet gears of the second planetary gear set orbit the sun gear of the second planetary gear set, with meshing teeth. The sun gear of the second planetary gear set is rigidly attached to the outer output shaft, such that when the sun gear of the second planetary gear set rotates, it causes the outer output shaft to rotate. The outer output shaft is hollow, and the sun gear of the second planetary gear set also has a hollow center so that the inner output shaft, which is rigidly attached to the sun gear of the first planetary gear set, may pass through the center of the second planetary gear set without interacting with it, emerging from the second planetary gear set as the inner output shaft, within (and parallel with, along the centerline) the outer output shaft.
In this embodiment, when both annular gears are held static, both output shafts rotate at the same angular velocity, moving in unison. The rotation of the input shaft, which is the same as the rotation of the inner output shaft since they are both rigidly connected to the sun gear of the first planetary gear set, is transmitted through the AMT via the sun gear in the first planetary gear set, which drives the planet gears of the first planetary gear set to rotate in orbit around the sun gear of the first planetary gear set and within the annular gear of the first planetary gear set, thereby driving the planetary carrier (and the planetary gear array as a whole) of the first planetary gear set. The planetary carrier (and the planetary gear array) of the first planetary gear set then drives the planetary gear array of the second planetary gear set, since the planetary carrier of the first planetary gear set is rigidly attached to the planetary carrier of the second planetary gear set (such that the planet gears of the second planetary gear set rotate in unison with the planet gears of the first planetary gear set), causing the sun gear of the second planetary gear set, and thereby the outer output shaft, to rotate.
Since all of the gears in both of the planetary gear sets are identical (matching with their sister in the other planetary gear set), when the annular gears are held fixed, the input rotation from the input shaft is transferred through the AMT without any change so that the inner output shaft and the outer output shaft rotate at the same angular speed, and there is no angular displacement between the two output shafts. But, if the annular gear of the second planetary gear set is rotated with respect to the annular gear of the first planetary gear set (or vice versa), then the outer output shaft will receive a proportional rotation (angular displacement) with respect to the inner output shaft. Once the angular relationship between the two annular gears has ceased to change, the two output shafts will again rotate at the same angular speed, but their angular relationship will have changed proportionally to the change in the angular relationship between the two annular gears (i.e. the angular displacement would remain). The angular change in relationship between the two output shafts is equal to the angular change in relationship between the two annular gears times a scaling factor, which is the number of teeth in an annular gear divided by the number of teeth in a planet gear.
In the second preferred embodiment, the input shaft is rigidly attached to the sun gear of the first planetary gear set, such that when the input shaft rotates, it causes the sun gear of the first planetary gear set to rotate. The sun gear of the first planetary gear set is also rigidly attached to the inner output shaft, such that the sun gear of the first planetary gear set is sandwiched between the input shaft and the inner output shaft (or, these three elements may be thought of as one, continuous element). The planet gears of the first planetary gear set are held in place around the sun gear (with meshing teeth) by the planetary carrier of the first planetary gear set, which is held static (while typically resting on bearings such that it does not interact with the input shaft). The annular gear of the first planetary gear set encompasses the planet gears (with meshing teeth) and is rigidly attached to the annular gear of the second planetary gear set, which encompasses the second planetary gear set. Thus, the annular gears of both planetary gear sets are linked and rotate as a single unit. The planet gears of the second planetary gear set are held in place within the annular gear of the second planetary gear set by the planetary carrier of the second planetary gear set, which is statically fixed (while typically resting on bearings such that it does not interact with the outer output shaft), except that the angular relationship between the two planetary carriers may be altered. The planet gears of the second planetary gear set surround the sun gear of the second planetary gears set (with meshing teeth), which is located at the center of the second planetary gear set. The sun gear of the second planetary gear set is hollow, such that the inner output shaft may pass through the second planetary gear set without interacting with it, and is rigidly attached to the outer output shaft, which is also hollow.
In this embodiment, when both planetary carriers are held static, both output shafts rotate at the same angular velocity, moving in unison. The rotation of the input shaft, which is the same as the rotation of the inner output shaft since they are both rigidly connected to the sun gear of the first planetary gear set, is transmitted via the sun gear, through the planet gears of the first planetary gear set, to the annular gear of the first planetary gear set. The planet gears do not orbit the sun gear because they are restrained by the static planetary carrier, so that the planet gears instead rotate in place, transmitting the driving force to the annular gear and causing the annular gear to rotate. Since the annular gear of the first planetary gear set is rigidly attached to the annular gear of the second planetary gear set, the annular gear of the second planetary gear set is driven in lockstep with the annular gear of the first planetary gear set. The annular gear of the second planetary gear set acts upon the planet gears of the second planetary set, which are restrained by the static planetary carrier of the second planetary gear set so that they do not traverse the annular gear or orbit the sun gear, causing the planet gears of the second planetary gear set to rotate in place and thereby driving the sun gear of the second planetary gear set. The sun gear of the second planetary gear set drives the outer output shaft.
Since all of the gears in both of the planetary gear sets are identical (matching with their sister in the other planetary gear set), when the two planetary carriers are held fixed, the input rotation from the input shaft is transferred through the AMT without any change so that the inner output shaft and the outer output shaft rotate at the same angular speed and there is no angular displacement between the two output shafts. But, if the planetary carrier for the second planetary gear set is rotated with respect to the planetary carrier of the first planetary gear set (or vice versa), then the outer output shaft will receive a proportional rotation (angular displacement) with respect to the inner output shaft. Once the angular relationship between the two planetary carriers has ceased to change, the two output shafts will again rotate at the same angular speed, but their angular relationship will have changed proportionally to the change in the angular relationship between the two planetary carriers (i.e. the angular displacement would remain). The angular change in relationship between the two output shafts is equal to the angular change in relationship between the two planetary carriers times a scaling factor, which is the number of teeth in a planet gear divided by the number of teeth in an annular gear. This embodiment provides a greater mechanical advantage for the change inducing force than in the first embodiment, since a planet gear will always have fewer teeth than an annular gear.
The primary object of this invention is to allow a user to alter the angular relationship between two elements in a rotational frame. It is still another object to allow a user to alter the angular relationship between two elements in a rotating frame proportionately to a change in the relationship between two elements in a static reference frame. It is yet another object of this invention to employ direct mechanical coupling. It is yet another object to provide a durable, low-maintenance device for altering the angular relationship between two rotational elements, reducing wear and oscillation concerns. In addition to these general objects, the AMT can be used in several real-world applications. For example, an AMT device could be used for dispensing filament for a weed trimmer, for controlling the amplitude of shaking in a chute-type feeder for dry product, for operating a shutter in a motion picture camera, or for measuring torque. The use of the AMT to perform these various functions will be described in greater detail in the detailed description section below. These are only illustrative examples of possible uses for the AMT and are not exclusive; the AMT is not limited to these uses. These and other objects of the present invention will be more apparent to those skilled in the art field from the following detailed description of the AMT invention.